// 代码索引 3-4-2-1
#include <Eigen/Dense>
#include <iostream>
 
using namespace std;
 
int main()
{
    Eigen::MatrixXf m(3,3);
    m << 1,2,3,
         4,5,6,
         7,8,9;
    cout << "Here is the matrix m:" << endl << m << endl;
    cout << "2nd Row: " << m.row(1) << endl;
    m.col(2) += 3 * m.col(0);
    cout << "After adding 3 times the first column into the third column, the matrix m is:\n";
    cout << m << endl;
}